1. Field of the Invention
The invention relates to a roof module for a motor vehicle with an outside roof skin and layers of composite materials located on the vehicle interior side and a process for producing a multilayer roof module for a motor vehicle with an outside roof skin and layers of composite materials located on the vehicle interior-side.
2. Description of Related Art
Roof modules as are known, for example, from published European Patent Application EP 0 960 803 A2, constitute motor vehicle roofs which have been produced separately from the motor vehicle body and which are made sandwich-like with a roof skin and an underlying plastic layer made, for example, of foam plastic.
Published European Patent Application EP 0 995 667 A1 discloses a roof module as a composite component for motor vehicles, the roof module being composed of the outside roof skin and a reinforced plastic layer connected to it on the vehicle interior side for purposes of increasing the buckling stiffness and the overall strength. The plastic layer is made of a PUR foam which is formed from polyol and an isocyanate portion in a mixing ratio from 1 to 2. The mixing of the two plastic components with glass fiber reinforcement takes place using the long fiber injection (LFI) process in which PUR-wetted glass fibers are blown by compressed air into a negative mold already laid out with the outside skin. Roof modules which have been built up in this way do not have high stiffness and do have a total weight prevailing as a result of the of the high proportion of polyurethane (PUR).
German Patent DE 32 02 594 C2 and counterpart U.S. Pat. No. 4,475,765 disclose a roof module with an airtight and watertight outside roof layer, a middle, inherently stiff honeycomb/structure layer, with aluminum or cardboard ridges or semihard foam and nonwoven structures, a semistiff, porous inside layer and a cushion and/or decorative layer. One such multilayer roof module is produced using a hot pressing process. These roof modules based on a honeycomb or sandwich structure have the advantage that, as a result of the honeycomb layer which acts as the stiffening layer and carrier layer for other layers, they have higher stiffness with a lower overall weight. Production of multilayer roof modules of this type based on a honeycomb structure is time-consuming and complicated since generally glass fiber mats which extend on either side of the honeycomb layer are difficult to handle. Furthermore, these glass fiber mats are expensive as compared to glass fibers as are used in the LFI production process. In addition, positioning of the honeycomb layer within a negative mold which is used for carrying out the following pressing processes is generally complex and time-consuming.